On 03/21/2014 11:41 AM, Michael Kerrisk (man-pages) wrote:
Peter, do you agree that Linux appears to differ from POSIX here? (Not
sure if you tried my test program to verify...)
I did run the test program to validate that it's observed behavior is that
implemented by Linux, with which I'm very familiar.
I don't have a test setup for other *nixes.
I would be interested to know the results of
./noncanonical 0 5 3 0
hello
Solaris 10:
read() completes when 5 bytes received.
OpenBSD 5.4
read() completes when 5 bytes received.
Ok, Linux does the same.
and
./noncanonical 0 5 3 2
hel
Solaris
read blocks()
OpenBSD
read blocks
If you type fast, Linux will complete this read() with 3 bytes.
Plus my test case where Linux differs:
./noncanonical 100 5 3 0
Linux: read() returns after 3 bytes input
Solaris: read() returns only after 5 bytes input
OpenBSD: read() returns only after 5 bytes input
Ok, thanks for testing.
on other platforms.
With respect to POSIX compliance, it's hard to say. I'm not sure the
spec contemplates the degenerate case where max bytes < MIN. And
Well, given the way the other implementations behave, I think it does
contemplate it, because it carefull avoids talking about the number of
bytes requested by read() in that case.
I agree that's certainly a valid interpretation.
I'll go back and see if this is a regression but I doubt it.
specifically
with regard to terminal i/o behavior, POSIX is essentially ex post facto,
and is really documenting existing behavior.
Other than the degenerate case of max bytes < MIN, is there any other
variation between Solaris and Linux in non-canonical mode?
The only one I've seen is the one I noted. I haven't tested too
exhaustively though.
Thanks again. Please feel free to direct mail my way if you find other
variation.
Regards,
Peter Hurley
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